Genotypic variation in cadmium accumulation by seed of linseed, and comparison with seeds of some other crop species

Abstract

The accumulation of cadmium (Cd) in plants is a health issue because a range of grain and vegetable crops can accumulate levels of Cd that are in excess of limits set by the World Health Organization and individual countries. Many Australian agricultural soils used to produce confectionery linseed have a history of intensive use of Cd-contaminated phosphatic fertilisers and this, combined with soil properties such as high chloride salinity, can result in enhanced availability of Cd to crops. We investigated genotypic variation in Cd accumulation in seed of 17 linseed and Linola (termed linseed) lines from Australia and elsewhere in a glasshouse study using a soil from southern Australia that had a history of the application of Cd-contaminated phosphatic fertiliser. Canola, Indian mustard, lupins, and wheat were also included in the study for comparison. Under the experimental conditions, Cd concentrations in seed of all but one of the linseed lines exceeded the maximum permitted concentration (MPC) of 250 µg/kg for confectionery linseed traded on the international market. There was a 2.3-fold variation in seed Cd concentrations between all the linseed lines (range, 233–545 µg/kg). Linseed lines from Australia and overseas were equally capable of accumulating Cd in seed. Brown-seeded and golden-seeded lines accumulated similar concentrations of Cd. Canola, Indian mustard, lupins, and wheat accumulated about 10-fold lower concentrations of Cd in seed than linseed, and did not exceed Australian or other MPCs. There was little difference in Cd concentrations between the seed and de-seeded capsules of linseed, but a large difference in Cd concentration between the seed and de-seeded fruit parts of the other crops. The mean seed to de-seeded fruit part Cd concentration ratio for linseed was 0.87 : 1 compared with a ratio of 0.35 : 1 for the other crops, suggesting that linseed has comparatively ineffective barriers discriminating against the transport of Cd to seed.

Analysis of seed lots of confectionery linseed sampled from a grain receival depot showed that seed lots from farms in Victoria (range 140–560 µg Cd/kg) had 5-fold greater Cd concentrations than those from farms in New South Wales (range 20–160 µg/kg). This is presumably due to a more intensive history of the application of Cd-contaminated phosphatic fertiliser to pastures and crops in Victoria, as well as differences in environmental and soil conditions.